I don't think Ancient Empires was cancelled; there was another mod
that was cancelled that was going to remake AoE1 in AoE3.
Anyway, we don't even know the timeline yet of AoE4, and:
- I really don't think it's going to focus on the same era. For whatever reason, the latter half of the 19th century that this mod primarily covers hasn't entered into popular culture to the extent that earlier time periods (Classical antiquity, Medieval period, Age of Exploration/Napoleonic era) have, or the later World War years. Therefore AoE4 will probably skip over much of said time period (which AoE3 already partially covered and this mod just expanded on) and start with the more popular World Wars, like I said.
- AoE4 isn't coming out for awhile. My guess is a long time, with all the other AoE projects they've announced going on simultaneously.
Either way, there's no reason to cancel this mod prematurely, if at all.